null 和 typeof与 instanceof

typeof(null) 返回 object

null instanceof Object  返回 false

因为null作为js数据类型中的一种，本来就不是object？

至于为何typeof（null）返回的是object,这个和typeof的定义有关

​​​​​​​

11.4.3 The typeof Operator
The production UnaryExpression : typeof UnaryExpression is evaluated as follows:
1. Evaluate UnaryExpression.
2. If Type(Result(1)) is not Reference, go to step 4.
3. If GetBase(Result(1)) is null, return "undefined".
4. Call GetValue(Result(1)).
5. Return a string determined by Type(Result(4)) according to the following table:
Type Result
Undefined "undefined"
Null "object"
Boolean "boolean"
Number "number"
String "string"
Object (native and
doesn’t implement
[[Call]])
"object"
Object (native and
implements [[Call]])
"function"
Object (host) Implementation-dependent